Preparation and characterization of photo-cross-linked thermosensitive PNIPAAm nanogels

Thermosensitive nanogels were prepared from photo-cross-linkable copolymers of N-isopropyl-acrylamide (NIPAAm) and 2-dimethylmaleinimido ethylacrylamide (DMIAAm). The colloidal nanogels were formed by UV-irradiated solutions of thermosensitive polymers in water at 45 °C. The size of nanogels could be controlled by the concentration of photopolymer solutions, the amount of chromophore DMIAAm in the photopolymer chains, and sodium dodecyl sulfate (SDS) concentrations. Analytical ultracentrifugation could reveal the degree of swelling of the different nanogel preparations, confirming the data from dynamic light scattering. In addition, the quantitative determination of un-cross-linked polymer species was possible. Even the determination of the degree of swelling distribution was reported for a nanogel for the first time. Hydrogel particles could be prepared with low SDS concentration or even in the absence of a surfactant. Therefore, the effects on swelling produced by the addition of alcohols to these nanogels could be investigated, excluding the influence of SDS on the swelling behavior of these nanogels. © 2006 American Chemical Society.